A Stimpmeter is a simple tool used to measure the speed of putting greens - how easily a golf ball rolls across the surface of the green.
The Stimpmeter is a very low-tech device, essentially just a small, metal ramp that is angled down to a flat part of a putting green. How far the golf ball rolls across the green results in the "Stimp rating" of the green.
Stimp ratings in the single digits are considered slow to moderate-paced greens; Stimp ratings in the double digits are considered quick to fast greens.
THE STIMPMETER'S SPECIFICATIONS AND HOW IT WORKS
Here are some specifics about how the Stimpmeter is built and works:
Stimpmeters were originally wooden, modern Stimpmeters are made of aluminum.
They are 36 inches long.
Working on a flat portion of the green, the superintendent or other course or tournament official places a golf ball at one end in a notch about six inches from that end.
The person using the Stimpmeter slowly raises that end (by hand) until, when the device reaches an angle of 22 degrees, gravity causes the golf ball to release from the notch.
There is a groove, or channel, down the center of the Stimpmeter, which keeps the ball on track as it rolls down.
When the golf ball exits the ramp, it rolls out across the green.
How far the ball rolls before stopping becomes the "Stimp rating," indicating green speed. If the golf ball rolls nine feet, the Stimp rating is 9; if it rolls 11 feet, the green speed rates at 11.
WHO INVENTED THE STIMPMETER?
You might have noticed that "Stimpmeter" is capitalized; that's because the word is an eponym. That is, its name comes from the name of its inventor.
The inventor of the Stimpmeter was Edward S. Stimpson. Stimpson was an accomplished amateur golfer; he won the Massachusetts Amateur Championship in 1935.
And that was the same year Stimpson invented the simple tool for determining green speeds that bear his name.
After watching golfers who were flummoxed by the speeds of the greens during the 1935 U.S. Open at Oakmont Country Club, Stimpson realized that golf course superintendents needed a way to measure green speeds in order to ensure that each green on a golf course rolled at the same speed.
USGA'S ADOPTION OF THE STIMPMETER
Stimpson created his original Stimpmeter in 1935, and some golf courses began using it here and there soon after.
But the Stimpmeter wasn't used in an organized or official way by the USGA until 1976. In 1978, the Stimpmeter was finally adopted by the USGA for use at golf courses around the United States, and the American governing body began making them available to courses, along with instructing superintendents in their use. The Stimpmeter's use spread around the world in the years after. (The USGA prints an instruction pamphlet (.pdf file) on using the Stimpmeter for golf courses.)
The Stimpmeter was essentially unchanged for decades after its invention. But in 2012, a small modification was made to take into account the fact that modern putting greens sometimes don't have flat areas large enough to allow a full roll-out by a golf ball released from a Stimpmeter.
Today there is another notch on the reverse side of the Stimpmeter, halfway down the ramp. The process is the same, but the golf ball rolls half as far when this notch is used. The superintendent then doubles the result - if the ball rolls 5 feet using this option, the green speed rates a 10 - to get the Stimp rating.